This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A series of [Ru(tpy)(L2)(DMSO)]1+/2+ (tpy = terpyridine, L2 is a bidentate ligand, DMSO = dimethylsulfoxide) complexes has been developed, some of which display linkage isomerization of the DMSO ligand upon irradiation with visible light. The photoisomerization takes place on the excited state surface originating from the MLCT transition to the terpyridine ligand, which is in turn mediated by the bidentate L2 ligand. The difference in reactivity between complexes with varying L2 ligands can be investigated by probing the electronic structure surrounding the Ru-S and Ru-N bond interactions. Thus we will investigate the electronic structure of this class of phototriggered molecules using a combination of Ru K- and L-edge as well as ligand K-edge XAS.